Field of the Invention
Description of the Prior Art
In conventional two-stage connecting heads, a polygonal ball head of a supporting rod is received in a receiving slot of a working head, and the shape of the receiving slot is polygonal to correspond to the polygonal ball head. Through a connecting structure, when the supporting rod is pressed, it can be fixedly disposed to the working head; and when the supporting rod is pulled, it is pivotally swingable relative to the working head. Such type of conventions is disclosed in TW566284 and TWM357344.
In TW566284, because the inner wall of the receiving slot is polygonal, the inner wall of the receiving slot and the polygonal ball head are in face-face contact. When an electronic driving device drives the supporting rod to rotate relative to the working head in high speed, the polygonal ball head and the receiving slot may be deadlocked due to great friction, and the electronic driving device and the two-stage connecting head may be damaged. In addition, even if the polygonal ball head and the receiving slot are not deadlocked, the friction during the process wastes energy, causes low efficiency and troubles users.
In TWM357344, a lateral wall of the receiving slot has a plurality of protruding edges corresponding to the polygonal ball head. The protruding edges are arranged on the lateral wall of the receiving slot in intervals. A number of the protruding edges correspond to a number of angles of the polygonal ball head. Each protruding edge has an arc connecting face provided for connecting to the polygonal ball head so as to allow the supporting rod to rotate co-movably with the working head and improve the deficiencies of TW566284.
However, no matter in TW566284 or TWM357344, a blocking flange which can restrict each corner portion of the polygonal ball head is not disposed, so during high-speed working process, the driving head disassembles easily, and problems such as poor efficiency, interruption and danger may happen during the process.
U.S. Pat. No. 1,070,233 discloses that the inner sleeve is provided with a through hole which is for the shaft to insert therein and is much less than the opening of the outer sleeve in radial dimension, so that the shaft within the inner sleeve is comovable with the inner sleeve and cannot engage with the outer sleeve, and the inner sleeve cannot used for a driving head tool having a polygonal ball head. In fact, the shaft is fixedly integrated with the inner sleeve and cannot be changed.
The present invention is, therefore, arisen to obviate or at least mitigate the above-mentioned disadvantages.